1. Field of Invention
This invention relates generally to industrial manufacture equipment and, more particularly, to a control system and method for controlling the properties of a sheet being manufactured by the industrial manufacture equipment using a wireless network of actuators capable of peer-to-peer communication.
2. Description of Related Art
Modern industrial manufacture equipment for the manufacture of sheet products, such as paper, uses a series of actuators distributed over the sheet being manufactured to adjust the various properties of the sheet, such as caliper, moisture content, etc. The actuators control properties over the length of the sheet in the direction the sheet is moving on the equipment (the machine direction (MD)) and also across the width of the sheet in the cross direction (CD). Various sensors or scanners are positioned at locations along the sheet under manufacture to scan properties of the sheet and collect data to establish a profile across the sheet with respect to a particular property. A remote device or supervisory controller processes the collected data and produces control information (control actions, setpoints, status, positions). This control information is fed back to the appropriate actuators to adjust the properties under their influence toward a desired goal.
Typically, cross direction profile control and machine direction control is performed by the supervisory computer and an independent, distributed set of regulatory controllers performing basic actuator regulation in accordance with instructions from the supervisory computer. Profiles and other measured values are sent to the supervisory computer, which generates setpoints and sends them to the various regulatory controllers, which are responsible for moving and maintaining the associated actuators at the desired supervisory setpoint.
However, there is little overall coordination of all the CD actuators controlling all the various property profiles such as weight, moisture, and caliper. In general, there is little or no coordination between MD properties and CD properties performed by the supervisory computer.
U.S. Pat. No. 6,094,604, assigned to Honeywell Measurex Devron Inc. describes a control system and method with a network of intelligent actuators in a sheet-making machine that communicates control information to each other and is connected to each other via a bus.
Furthermore, U.S. Pat. No. 5,771,174, assigned to Measurex Corporation describes LAN (local area network) to tie a series of actuators (across the paper machine width) together and to also permit communication with the supervisory or host control system. Each actuator has an electrical connection coupled to a controller with a network bus. Communications between the actuator controllers and a gateway, as well as peer-to-peer communications between adjacent actuator controllers, take place along the network bus. The bus is a six-wire bus distributing power to the actuator controller and communications to the actuator controllers and to the gateway. Physically, the bus consists of one unshielded twisted pair of wires. This bus consists of one or more free-topology channels with a maximum of 62 actuators communicating on one channel.
However, both of these systems use a bus or cable to facilitate communication in the network. This causes a significant manpower for installation, maintenance and troubleshooting. Additionally, there is a significant cost for the installation. Further, the networking routing would require significant overhead and/or a separate device dedicated to control the routing. Additionally, if bus malfunctions, the entire bus must be replaced.
Accordingly, there is a need to reduce the cost and simplify the maintenance for the actuator network.